Via formation and via filling is used in traditional semiconductor manufacturing. These vias are formed in material such as silicon wafers, silicon substrates, or in PCB boards. These discrete substrates used in the electronics and semiconductor industry are rigid and thus, almost none of the methods developed for via formation or via filling in these industries are adapted for use on a continuously moving, roll-to-roll flexible substrate. Instead, these traditional methods are based on step-and-repeat techniques where the discrete workpieces are transported to a work zone, indexed to the proper location so that the via formation or clearing devices can operate, and then moved on while another work piece is then brought into position in the work zone.
Such a traditional step-and-repeat methodology, though suitable for discrete substrates, would significantly hamper a continuously moving, roll-to-roll manufacturing system. A careful review shows that a majority of the time and in some situations up to 90% of the time associated with these step-and-repeat systems is spent on transporting the substrates to the appropriate location, indexing them to the proper position for processing, and then moving them out while another substrate is moved into position. Thus, in terms of actual material deposition time, some traditional systems only utilize 1/10 of the deposition capacity as much of the processing time is devote to substrate transport and indexing. The material in such traditional systems cannot occur until these other steps are completed.
A typical material deposition system employs one or several deposition heads that are moved through the process area using XY linear stages. They are sufficiently precise, but have low throughput for continuous large area or high throughput processing. They are built with batch processing in mind, where the high density of vias per unit area is so high that indexing and alignment times are small relative to processing time. For a state of the art system using the batch-processing paradigm described above, approximately 90% of the cycle time will be consumed by alignment, indexing of the web, and indexing of the deposition.
A central challenge in cost-effectively depositing material into designated locations such as for via filling involves being highly accurate, tightly toleranced while not slowing and/or stopping the elongate substrate during processing. A system similar to a mark-on-the-fly (MOTF) architecture, in which the material is continuously moving under the deposition head or nozzle system may present some improvements. Despite the potential advantages of mark on the fly for application in roll-to-roll systems, its use was discouraged by experts in the field. In part, the reason for this is that traditional mark-on-the-fly architectures cannot mark or deposit at high precision relative to fast-moving, variable incoming material. The known MOTF systems would not be sufficiently capable and would most likely create numerous issues of inaccurate depositions.
Traditional mark-on-the-fly systems may operate in several modes, but the failures or drawbacks of the two most common will be described herein. In one mark on the fly architecture, an encoder is used to track the velocity of the web/part, and an external trigger is used to initiate the marking sequence. This technique is suitable for marking barcodes or part numbers on products, but it is completely unsuitable for our application, since it has no ability to precisely locate the mark relative to a predefined location on the web. In a different architecture, a camera is used to photograph the position of a fiducial, and an encoder is used to measure velocity. This technique represents a step up in precision relative to the first model, but traditional alignment and control algorithms, as well as numerous other details, make traditional implementations of this design slow and inaccurate.
Thus, there is a need for an improved high speed, high accuracy material deposition system.